Recently, with the advance in nanotechnology, a raw-material powder is sought to have a smaller particle size. The target of research and development is shifting from submicron particles to nanoparticles. Particularly, nanoparticles of 20 nm or smaller are known to demonstrate a peculiar electromagnetic effect along with change in an electronic state and also to have excellent properties, which a bulk material does not have, owing to an increased percentage of surface atoms and so on. For this reason, for example, silicon fine particles are expected to be used for a light-emitting element and other applications.
As a method for producing light-emitting silicon fine particles that have properties to emit visible light, a production method described in Patent Document 1 is known. In this production method, a mixture containing a silicon source and a carbon source is baked in an inert atmosphere. A reaction gas generated by the baking is rapidly cooled to obtain a composite powder of silicon (Si), silicon monoxide (SiO), and silicon dioxide (SiO2). The obtained composite powder is immersed in an etching solution containing hydrofluoric acid and an oxidant. Thus, light-emitting silicon fine particles are produced.